Utilization of ladybird beetles to curb aphids in strawberry high tunnels: preliminary results

Authors: Riddick, Eric

Submitted to: Midsouth Entomologist
Publication Type: Abstract Only
Publication Acceptance Date: 10/18/2016
Publication Date: 11/1/2016
Citation: Riddick, E.W. 2016. Utilization of ladybird beetles to curb aphids in strawberry high tunnels: preliminary results. Midsouth Entomologist. 9(2):80.

Interpretive Summary:

Technical Abstract: Native and exotic aphid species continue to pose a threat to the successful cultivation of small fruits in greenhouses, glasshouses, and high tunnels throughout the World. There is considerable interest in using biological controls (predators and parasitoids) to manage aphids in lieu of synthetic insecticides. The aim of this research is to evaluate the effect of predatory ladybird beetles to curb aphid populations on cultivated strawberry (Fragaria x ananassa Duchesne) in high tunnels in Stoneville, Mississippi, USA. The hypothesis that ladybird beetles can reduce aphid densities on strawberry plants was tested. In April 2016, plants were potted into two-liter nursery pots, containing organic potting mix, and arranged in rows on four metal benches in four replicate high tunnels (18 ft. wide, 24 ft. long). By early June, we detected one species of aphid (species undetermined), at extremely low densities on “daughter” plants, still attached by runners (stolons) to “mother” plants, in one high tunnel. To ensure that all high tunnels had aphids, we distributed infested daughter plants into the other high tunnels. On 12 August, we randomly selected 30 daughter plants, still attached to mother plants, and recorded the number of aphids (wingless adults, and nymphs) on them. On 15 August, we released second instar larvae of the ladybird Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae), from our lab colony, at a ratio of 1 C. maculata larvae: 10 aphids, onto the benches containing the selected daughter plants, in three of the four high tunnels. Thereafter, aphid densities were recorded on 19 and 25 August, and 1, 8, and 15 September. The results revealed a rapid decline in aphid density in test high tunnels within four days after releases. On 19 August, aphid reduction was 71%, 86%, and 97% in the three test high tunnels; aphid reduction was 35% in the one control high tunnel. Interestingly, by the last day of sampling (15 September), aphid reduction was over 96% in test and control high tunnels. Host plant resistance and immigrating ladybirds (e.g., Scymnus species) might have contributed to aphid reduction in the control high tunnel by the last day of sampling.